Control device for an automatic transmission

ABSTRACT

A control device for an automatic transmission which prevents an automatic transmission from executing a “busy-shift” caused by a lower gear ratio of the highest gear, and which reduces revolutions of a driving power source at high speed. The control device includes an automatic shift mode, an independent manual shift mode, and a highest gear control means. The automatic shift mode automatically determines a gear ratio of the automatic transmission on the basis of a driving condition of a vehicle having the automatic transmission. The manual shift mode determines a gear ratio of the automatic transmission by a driver&#39;s intention. The highest gear control means controls the automatic transmission, so that the smallest gear ratio set by the manual shift mode is smaller than the smallest gear ratio set by the automatic shift mode. If the gear ratio of the highest gear of the automatic shift mode is not so small, a shift caused by a change of a driving condition does not easily occur. The busy-shift can be avoided in the automatic transmission. Although a smaller gear ratio can not be adopted in the automatic shift mode, it can be set if the manual shift mode is selected. Therefore, revolutions of a driving power source are reduced and a fuel consumption can be improved.

FIELD OF THE INVENTION

[0001] The present invention relates to an automatic transmission inwhich a gear ratio can be set on the basis of a driving condition, forexample a load against a power source of a vehicle, a vehicle speed,etc. Especially, this invention relates to a control device of theautomatic transmission in which a gear ratio of overdrive gears can beset.

BACKGROUND OF THE INVENTION

[0002] A power source, for example an internal combustion engine or/andan electric motor, etc. are installed in a vehicle. Sincecharacteristics of such a power source do not necessarily satisfy anoutput power required over the entire range of a vehicle from startingto high speed running, a transmission is mounted in the vehicle inaddition to the power source in order to increase or reduce drivingtorque or a rotation speed of the power source. As one example of thetransmission, an automatic transmission, which is automaticallycontrolled to shift gears according to a running condition of thevehicle, is adopted in many cases. Furthermore, in accordance with arequired improvement of power output characteristics or a requiredreduction of fuel consumption of the vehicle, the smallest gear ratio ofthe automatic transmission tends to be smaller than 1. A revolution ofthe power source can be reduced in high speed running of the vehicle,owing to the above-mentioned automatic transmission.

[0003] In the aforementioned background, an automatic transmission witha plurality of shift gears tends to multiply the number of the shiftgears in these days. One example of such an automatic transmission isshown in Japanese Laid-Open Patent Application No. 8-177994. Theautomatic transmission shown in this Patent Application, has a structuremainly having 3 sets of planetary gears, and 5^(th) gear and 6^(th) gearare respectively overdrive gears. Furthermore, rotating speeds ofrotating members of the automatic transmission are restrained.

[0004] In the automatic transmission with six forward gears, the gearratio of the highest gear (i.e. the smallest gear ratio of the automatictransmission) is smaller than a gear ratio of the highest gear ratio ofan automatic transmission with five forward gears. Since an enginerevolution in a vehicle having the automatic transmission can bereduced, the fuel consumption of the vehicle is improved during highspeed driving. Furthermore, since excessive high rotating speeds ofrotating members can be avoided, a durability of the automatictransmission is improved.

[0005] Since the gear ratio of 6^(th) gear, as the highest gear, issmall, however, the driving torque of the vehicle in 6^(th) gear issmall. The 6^(th) gear is set when a load of an engine is low (i.e. athrottle angle or accelerator angle is low), and a speed of the vehicleis rather high. Consequently, even though the speed of the vehiclereduces only a few, or the engine load increases only a few bydepressing an accelerator pedal of the vehicle, a driving condition ofthe vehicle enters into the 5^(th) gear range, and a down-shift of theautomatic transmission from 6^(th) gear to 5^(th) gear occurs. If thespeed of the vehicle is higher or the engine load is lower by pullingback the accelerator pedal after the down-shift happens, the drivingcondition of the vehicle again enters into the 6^(th) gear range, andthe up-shift of the automatic transmission occurs.

[0006] As mentioned above, from the viewpoint of fuel efficiency of thevehicle it is advantageous that the automatic transmission hasmultiplied gears. On the contrary, however, an up-shift or a down-shiftof the automatic transmission frequently occurs, caused by only a littlefluctuation of a driving condition of the vehicle. Such a phenomenon iscalled “busy-shift”. That is, a driver of the vehicle might feeluncomfortable because of the busy-shift.

SUMMARY OF THE INVENTION

[0007] It is thus one object of the present invention to solve theaforementioned problems. That is, the object of the invention is toprovide a control device for an automatic transmission which prevents anautomatic transmission from the above-mentioned busy-shift caused by alower gear ratio of the highest gear, and which enables to effectivelyand practically use a gear ratio of the highest gear.

[0008] A control device for an automatic transmission comprises aselecting device and a highest gear control means. The selecting deviceselects an automatic shift mode or an independent manual shift mode. Theautomatic shift mode automatically determines a gear ratio of theautomatic transmission on the basis of a driving condition of a vehiclehaving the automatic transmission. The manual shift mode determines agear ratio of the automatic transmission by a driver's intention. Thehighest gear control means controls the automatic transmission so thatthe smallest gear ratio set by the manual shift mode is smaller than thesmallest gear ratio set by the automatic shift mode.

[0009] If the gear ratio of the highest gear of the automatic shift modeis not so small, a shift caused by a change of a driving condition doesnot easily occur. That is, the busy-shift can be avoided in theautomatic transmission. Although the further small gear ratio can not beadopted in the automatic shift mode, it can be set if the manual shiftmode is selected. In this case, revolutions of a driving power source isreduced and fuel efficiency can be improved.

[0010] A control device for an automatic transmission comprises a shiftdevice and a means for guiding the shift device. The shift deviceselects a neutral position, a highest gear prohibition position, ahighest gear permission position, and a middle speed position. In theneutral position, the automatic transmission does not output a torque toan output shaft of the automatic transmission. In the highest gearprohibition position, the highest gear of the automatic transmission isprohibited. In the highest gear permission position, the highest gear ofthe automatic transmission is allowable. In the middle speed position, agear ratio can be set between the largest gear ratio and a predeterminedgear ratio larger than the smallest gear ratio of the highest gearprohibition position. The guiding means guides the shift device along apath to the neutral position, a path to the highest gear permissionposition, and a path to the middle speed position. Each path separatelybranches off from the highest gear prohibition position and is connectedto the neutral position, the highest gear permission position, and themiddle speed position.

[0011] Since the highest gear is not set in the highest gear prohibitionposition which is selected by moving a shift device from the neutralposition, a slight change of a driving condition in high speed runningdoes not cause a down-shift of the automatic transmission. Consequently,the busy-shift can be avoided. On the contrary, since the highest gearpermission position is selected by further moving the shift device, andthe highest gear in the highest gear permission position isintentionally set by a manual operation. In other wards, since thehighest gear can intentionally be released, the busy-shift can beavoided by the manual operation. Furthermore, even if a gear shifthappens at the highest gear running in the highest gear permissionposition, a driver does not feel uncomfortable, because the driverselects such a position and is ready for the down-shift.

[0012] A control device for an automatic transmission comprises aplurality of overdrive gears and a highest gear prohibition means. Thehighest gear prohibition means prohibits the smallest gear ratio of theoverdrive gears of the automatic transmission when a speed of a vehiclehaving the automatic transmission is equal to or over a predeterminedvalue and a running resistance of the vehicle is equal to or over apredetermined value.

[0013] Since the automatic transmission has a plurality of overdrivegears, revolutions of a driving power source can be reduced by selectingthe smaller gear ratio among the overdrive gears in high speed driving.The fuel efficiency of the vehicle is then improved. On the other hands,when the vehicle runs on a slope at high speed and a running resistanceis high, the smallest gear ratio is prohibited. Since the gear ratio isnot so small in this case, a down-shift does not easily occur. Thereforethe busy-shift can be avoided.

[0014] A control device for an automatic transmission is installed in avehicle having a driving instruction system. The driving instructionsystem detects a predetermined scheduled course for driving the vehicleand a road condition of the predetermined scheduled course. The controldevice comprises a means for controlling a gear shift of the automatictransmission and a highest gear prohibition means. The means controls agear shift on the basis of the road condition of the predeterminedscheduled course. The highest gear prohibition means prohibits thesmallest gear ratio of the overdrive gears of the automatictransmission, when the vehicle is driven on the predetermined scheduledcourse, a speed of the vehicle is equal to or over a predeterminedvalue, and a running resistance of the vehicle is equal to or over apredetermined value.

[0015] When a road ahead for high speed running is detected in apredetermined scheduled course and a rather high torque is necessary forthe vehicle to run on the road, the highest gear of the automatictransmission is prohibited before the vehicle gets to the road. Sincethe needed driving torque is secured when the vehicle runs on the road,it can be avoided in advance that the vehicle speed is slower and ashift-down occurs or an up-shift after the shift-down (that is thebusy-shift) occurs.

[0016] A control device for an automatic transmission is installed in avehicle which has a following device. The following device followsanother vehicle ahead and comprises a shift device and a highest gearprohibition means. The highest gear prohibition means prohibits thesmallest gear ratio of the overdrive gears of the automatic transmissionwhen the vehicle is driven by the following device.

[0017] Since the highest gear is not set when the vehicle followsanother vehicle, enough torque for driving is secured. Consequently, afollowing and response ability to the vehicle ahead can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features, advantages, and technicaland industrial significance of this invention will be better understoodby reading the following detailed description of a presently preferredembodiment of the invention, when considered in connection with theaccompanying drawing, in which:

[0019]FIG. 1 is a flowchart which explains one example of a controldevice for an automatic transmission as a first embodiment of thepresent invention;

[0020]FIG. 2 is a schematic skeleton drawing of an automatictransmission to which the control device can be adopted;

[0021]FIG. 3 is a schematic view of a power train including theautomatic transmission;

[0022]FIG. 4 is a diagram which shows an engagement and a disengagementof each clutch, brake, or one-way clutch for setting each shift gear andshift position of the automatic transmission;

[0023]FIG. 5 is a schematic drawing showing one example of each shiftposition of a shift device for the automatic transmission of the firstembodiment;

[0024]FIG. 6 is a schematic drawing which illustrates one example of adown-switch and an up-switch positions on a steering wheel;

[0025]FIG. 7 is a schematic drawing which shows each shift position ofanother shift device having an up-position and a down-position;

[0026]FIG. 8 is a diagram showing shift gears available in each shiftposition where a shift gear among a plurality of shift gears isavailable by a manual operation M position;

[0027]FIG. 9 is a diagram showing another type of shift gears where onlyone shift gear is respectively set by a manual operation in M position;

[0028]FIG. 10 is a diagram which shows a part of a shift pattern mapsetting a shift gear range of 6^(th) (Overdrive 2^(nd)) gear;

[0029]FIG. 11 is a diagram which shows a part of a lock-up pattern mapsetting a lock-up range in 6^(th) gear;

[0030]FIG. 12 is a block diagram showing input and output signals to anECU (Electric Control Unit) of the control device;

[0031]FIG. 13 is a schematic drawing showing each shift position of ashift device adopted to a control device of a second embodiment;

[0032]FIG. 14 is a flowchart which explains a control device for anautomatic transmission as a second embodiment of the present invention;

[0033]FIG. 15 is a schematic drawing showing another type of shiftpositions adopted to a control device of the second embodiment;

[0034]FIG. 16 is a schematic drawing showing each shift position of ashift device adopted to a control device of a fourth embodiment;

[0035]FIG. 17 is a diagram showing shift gears available in each shiftposition for the fourth embodiment;

[0036]FIG. 18 is a flowchart which explains a control device for anautomatic transmission as a third embodiment of the present invention;

[0037]FIG. 19 a flowchart which explains a control device for anautomatic transmission as a fourth embodiment of the present invention;

[0038]FIG. 20 is a diagram showing another example of shift gearsavailable in each shift position adopted to the fourth embodiment; and

[0039]FIG. 21 is a schematic view of a vehicle on which an automatictransmission with a control device of the first embodiment is mounted.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0040] In the following description and the accompanying drawings, thepresent invention will be described in more detail in terms of specificembodiments. An automatic transmission having a control device of thepresent invention is first explained. FIG. 2 is a schematic skeletonview which illustrates one example of the automatic transmission. Thisautomatic transmission comprises a main-transmitting device G1 and asub-transmitting device G2. The main-transmitting device G1 has two setsof single-pinion type planetary gears, one set of double-pinion typeplanetary gear, and a plurality of friction engaging means. Thesub-transmitting device G2 has a single pinion type planetary gear and aplurality of friction engaging means. In the automatic transmission, sixforward shift gears and one reverse shift gear can be set by thisstructure and by engaging or disengaging the friction engaging means.

[0041] First, the above-mentioned main-transmitting device G1 isdescribed. A first planetary gear 1 is a single-pinion type planetarygear having a sun gear S1, a ring gear R1, and a carrier C1. The carrierC1 comprises a plurality of pinions P1. The sun gear S1 rotates at thecenter circle of the first planetary gear 1 and engages the pinions P1.The ring gear R1 rotates at the outer circle of the first planetary gear1. The pinions P1 are disposed between the sun gear S1 and the ring gearR1. The pinions P1 rotate while moving along the outer circumference ofthe sun gear S1. The carrier C1 supports a rotational shaft of eachpinion P1.

[0042] In the same way, a second planetary gear 2 is a double-piniontype planetary gear having a sun gear S2, a ring gear R2, and a carrierC2. The carrier C2 comprises a plurality of pinions P2. The pinions P2,here, are different from the aforementioned pinions P1. The pinions P2comprise a double set of pinions. Each pinion of one set of pinionsrespectively engages each pinion of another set of pinions. The sun gearS2 rotates at the center circle of the second planetary gear 2 andengages the pinions P2. The ring gear R2 rotates at the outer circle ofthe second planetary gear 2. Two sets of pinions P2 are disposed betweenthe sun gear S2 and the ring gear R2. The pinions P2 rotate while movingalong the outer circumference of the sun gear S2. The carrier C2supports a rotational shaft of each pinion P2.

[0043] Furthermore, a third planetary gear 3 is a single-pinion typeplanetary gear having a sun gear S3, a ring gear R3, and a carrier C3.The carrier C3 comprises a plurality of pinions P3. The sun gear S3rotates at the center circle of the planetary gear 3 and engages thepinions P3. The ring gear R3 rotates at the outer circle of the thirdplanetary gear 3. The pinions P3 are disposed between the sun gear S3and the ring gear R3. The pinions P3 rotate while moving along the outercircumference of the sun gear S3. The carrier C3 supports a rotationalshaft of each pinion P3.

[0044] Each rotating member of the planetary gears 1, 2, and 3 isconnected together as follows. The planetary gears 1, 2, and 3 areco-axially disposed in order of 1, 2, and 3. The carrier C1 of the firstplanetary gear 1 is coupled to the carrier C2 of the second planetarygear 2, and they rotate as one body. The ring gear R1 of the firstplanetary gear 1 is coupled to the ring gear R2 of the second planetarygear 2, and the ring gear R2 is coupled to the carrier C3 of the thirdplanetary gear 3. All three of these members, R1, R2, and C3, rotate asone body. Furthermore, the sun gear S2 of the second planetary gear 2 iscoupled to the sun gear S3 of the third planetary gear 3, and theyrotate as one body.

[0045] Next, the friction engaging means in the main-transmitting deviceG1 are explained. An intermediate shaft 4 as a hollow or solid shaft isdeposited coaxial to the first planetary gear 1 in the front of thefirst planetary gear 1. The intermediate shaft 4 is selectivelyconnected to the sun gears S2 and S3 by engagement of a first clutch K1.The intermediate shaft 4 is selectively connected to the sun gear S1 ofthe first planetary gear 1 by engagement of a second clutch K2.

[0046] Furthermore, the intermediate shaft 4 is selectively connected tothe carrier C1 of the first planetary gear 1 and the carrier C2 of thesecond planetary gear 2 by engagement of a third clutch K3. Theseclutches K1, K2, K3 are required to have a capacity for transmittingtorque selectively. A multi-plate clutch by engaging or disengaging oilpressure, a dry type single plate clutch, or a one-way clutch isadequately adopted to each above-mentioned clutch.

[0047] A first brake B1 is provided for selectively stopping therotation of the sun gear S1 of the first planetary gear 1. A one-wayclutch F1 is deposited between the sun gear S1 and a second brake B2having a plurality of plates, and the one-way clutch F1 prevents the sungear S1 from rotating in a predetermined direction. The second brake B2is fixed by a fixing part 5 (for instance, a casing of the automatictransmission). A third brake B3 is deposited between the carrier C1 ofthe first planetary gear 1 and the fixing part 5. The third brake B3having a plurality of plates selectively stops a rotation of thecarriers C1 and C2 which are coupled together.

[0048] Furthermore, a fourth brake B4 is deposited between the ring gearR3 of the third planetary gear 3 and the fixing part 5. The fourth brakeB4 also having multiple plates selectively stops a rotation of the ringgear R3. A one-way clutch F2 is provided in parallel with the fourthbrake B4, and the one-way clutch F2 prevents the ring gear R3 fromrotating in a predetermined direction. An output shaft 6 is coupled tothe carrier C3 of the third planetary gear 3 in order to rotate as onebody.

[0049] Next, the sub-transmitting device G2 comprises one set of asingle pinion type planetary gear 7, and two conditions of high and lowgears can be set by the sub-transmitting device G2. That is, a carrierC0 is an input member, and an input shaft 8 is connected to the carrierC0. A multi-plate clutch K0 and a one-way clutch F0 are deposited inparallel together, between a sun gear S0 and a carrier C0. The carrierC0 supports pinions P0 which engages the sun gear S0 and rotates whilemoving along the outer circumference of the sun gear S0. The one-wayclutch F0 engages, when the sun gear S0 is about to relatively rotateagainst the carrier C0 in the normal direction. Furthermore, a brake B0having a plurality of plates is deposited between the sun gear S0 andthe fixing part 5. The brake B0 selectively stops the sun gear S0 fromrotating. A ring gear R0 is coupled to the intermediate shaft 4 includedin the main-transmitting device G1.

[0050] Furthermore, a torque converter 9 with a lock-up clutch 15 isprovided in the input side of the sub-transmitting device G2. Thistorque converter 9 is a conventional type and forms a sealed-upcontainer with a front cover 10 and a shell of a pump impeller 11. Thepump impeller 11 contains oil (automatic transmission oil, also calledAT fluid). In the container a turbine runner 12 is deposited facing thepump impeller 11, and the turbine runner 12 is connected to theabove-mentioned input shaft 8 as one body.

[0051] Furthermore, a stator 14 which is held by a one-way clutch 13 isdeposited in the rotating center circle of the torque converter 9between the pump impeller 11 and the turbine runner 12. The lock-upclutch 15 is deposited facing the inner face of the front cover 10, andthe lock-up clutch 15 can be engaged by contacting the front cover 10 ordisengaged by being apart from the front cover 10. The lock-up clutch 15directly connects the pump impeller 11 to the turbine runner 12. Thatis, when the lock-up clutch 15 engages, the pump impeller 11 and theturbine runner 12 rotate as one body.

[0052] Incidentally, a turbine rotation speed NT sensor 16 is providedfor detecting a turbine speed as an input rotation speed of theautomatic transmission, and an output rotation speed sensor 17 isprovided for detecting an output speed of the automatic transmission asa vehicle speed.

[0053] The above-mentioned automatic transmission is shown as At in FIG.3. The automatic transmission At is combined to an engine Eg (aninternal combustion engine or a diesel engine) at an output side of theengine Eg and they are installed in a vehicle (shown in FIG. 21).Incidentally, the automatic transmission At can be combined to the othertype of a power source, for example an electric motor in an electricpower source vehicle, a hybrid type power source having an engine and anelectric motor in a hybrid vehicle, etc. On the basis of a load of theengine Eg determined by an acceleration angle or a throttle angle, or adriving condition determined by a turbine rotation speed or a vehiclespeed, a shift gear of the automatic transmission At is electricallycontrolled according to a shift lever position. That is, an oil pressurecontrol device Bb is provided for electrically controlling supply orrelease of the oil pressure. Shifting a gear of the automatictransmission At is set by an ECU (Electric Control Unit) which receiveseach signal from each sensor shown in FIG. 12 and controls the oilpressure control device Bb.

[0054] The ECU mainly comprises a micro-computer, the same as aconventional electric control unit. The ECU determines a gear shift ofthe automatic transmission At, on the basis of an input signalindicating a driving condition, for example a vehicle speed V, anacceleration angle Acc, etc. and a shifting map which is memorized inadvance. The ECU also controls an engagement, a disengagement, or a halfengagement of the lock-up clutch 15. Half engagement, here, means acondition where clutch plates of a lock-up clutch slips and the lock-upclutch engages insufficiently.

[0055] A shift device Sr is provided for selecting a neutral position, adriving position, a reverse position, etc. A shift position of the shiftdevice Sr determines a supply or release of oil pressure in the oilpressure control device Bb. The shift device Sr is not only mechanicallyconnected to a predetermined valve in the oil pressure control deviceBb, but a switch or a sensor attached to the shift device Sr is alsoconnected to the ECU. An output signal of the switch or the sensor isinputted to the ECU.

[0056] When a forward driving position is selected in the shift deviceSr, each shift gear of the automatic transmission At is determined bysupply or release of the oil pressure to the aforementioned frictionengaging means by way of the oil pressure control device Bb, based onthe output signal of the ECU. D (Drive) position, P (Park) position inwhich the vehicle stops, R (Reverse) position in which the vehicle runsin the reverse direction, N (Neutral) position, etc. are selected by theshift device Sr. The supply or release of each friction engaging meanscontrolled by the ECU is shown in FIG. 4.

[0057] In FIG. 4, P, R, or N indicates a park, reverse, or neutralposition selected by the shift device Sr. Each gear from 1^(st) through6^(th) is determined when the forward driving position is set. ◯ showsan engaged condition of each friction engaging means, ⊚ shows an engagedcondition in an engine braking, and Δ shows an engaged condition whereno power is transmitted. Each vacant space shows a disengaged condition.

[0058] As shown in FIG. 4, six forward shift gears can be set in theautomatic transmission At. Each gear from 1^(st) until 4^(th) gear, and6^(th) gear is set by engaging the clutch K0 of the sub-transmittingdevice G2 (This condition is the low gear of the sub-transmitting deviceG2 and also a direct connection between the input shaft 8 and theintermediate shaft 4.) and by engaging or disengaging each frictionengaging means of the main-transmitting device G1. 5^(th) gear is set bythe direct connection of the G1 where the whole members of themain-transmitting device G1 rotates as one body, and by the conditionwhere G2 is set as the high gear. Each gear ratio of 5^(th) gear and6^(th) gear is less than 1, and such a condition of 5^(th) or 6^(th)gear is called an overdrive gear.

[0059] An automatic mode or a manual mode can be selected in theabove-mentioned automatic transmission At. In the automatic mode, ashift gear is determined on the basis of an engine load and a drivingcondition of a vehicle speed or a turbine rotation speed. In a manualmode, a shift gear is determined according to an operation of a driver.In one example of the manual mode, a shift range is selected by anoperation of a switch. The one example is shown in FIG. 5. Each shiftposition of the shift device Sr is shown in FIG. 5. Here, the upper sidein FIG. 5 is the front of a vehicle or the upper side of the vehicle. P(Park), R (Reverse), N (Neutral), and D (Drive) positions are disposedin a row in order as shown in FIG. 5. M position is located adjacent toD position in the width direction of the vehicle. “4” position isdeposited in the rear direction of the vehicle or downwards toward Mposition. “3” and “2” positions are located in order in the diagonallyrear or diagonally downwards toward “4” position. L position is providedadjacent to “2” position in the transverse direction of the vehicle.Each position is selected by moving a shift lever of the shift deviceSr. A guiding path 18 such as a groove for guiding the shift lever Lv,connects each above-mentioned position together.

[0060] M position is provided for changing a shift range by operating aswitch manually. A down-switch 19 and an up-switch 20 are provided, andthese switches can be operational when M position is selected. Positionsof these switches are determined appropriately. One example of thepositions is shown in FIG. 6, in which they are on spokes of a steeringwheel 21. It is available and convenient that the down-switch 19 is onthe front side facing a driver, and the up-switch 20 is on the reverseside.

[0061] It is also available that both of a shift position and a shiftrange are operated by moving the shift lever of the shift device Sr, asshown in FIG. 7. In this example, each position from P position to Lposition except M position is located in order in a line in thefront-rear direction or the up-down direction, and each position isselected by moving a shift lever of the shift device Sr. The guidingpath 18 such as a groove for guiding the shift lever, connects eachaforementioned position. M position is deposited adjacent to D positionin the transverse direction of the vehicle, and “+” (up) position and“−” (down) position are provided in both sides of M position in thefront-rear direction or in up-down direction. Although each switch isnot shown in FIG. 7, each switch on the up-down positions arerespectively deposited. An up (+) signal or a down (−) signal isoutputted in accordance with a switch-on of each switch by moving theshift lever.

[0062] Each above-mentioned shift position is for selecting a shiftrange where shift gears can be set, and the shift range of each positionis shown in FIG. 8. First, one gear from 1^(st) gear to 5^(th) gear isavailable in D position. One gear from 1^(st) to 4^(th) gear can beavailable in “4” position. One gear from 1^(st) gear to 3^(rd) gear isavailable in “3” position. In L position, only 1^(st) gear is set.

[0063] A shift gear which can be set in each position is determined bythe ECU on the basis of a driving condition such as an engine load or avehicle speed, and a gear shift to a suitable gear is executed. In theabove-mentioned way, when the shift lever is fixed to each position, asuitable gear is selected automatically according to the drivingcondition of the vehicle.

[0064] On the contrary, when M position is selected by moving the shiftlever from D position, each position is set by pushing the up-switch 20or the down-switch 19 or by moving the shift lever to “+” position or“−” position. That is, a manual operation is necessary in M position,and it is, then, called a manual mode. As shown in FIG. 8, six forwardshift gears including 6^(th) gear (also called the second overdrivegear) can be set in M position. In other wards, when M position ismanually shifted and up-switch 20 or “+” position is manually operatedin the condition that the vehicle runs in 5^(th) gear and the vehiclespeed increases, the up-shift from 5^(th) gear to 6^(th) gear can beexecuted.

[0065] When the down-shift switch 19 is manually operated or “−”position is selected in the case that M position is selected by theshift device Sr, a shift range is changed to the lower shift range. Thatis, the shift range is shifted to “4” range position, “3” rangeposition, “2” range position, and L range position in order. When theup-shift switch 20 is manually pushed or the shift lever is moved to “+”position from L range position, a position is changed to the highershift range in the reverse order. Each shift range in which a shift gearcan be available in this manual shift mode is the same as in theautomatic shift mode in this case. That is, each shift range havingautomatically selected gear ratios is selected by a driver's intentionin the manual shift mode. Namely, the driver's intention can bereflected in the manual shift mode. Each shift range is controlled bymoving a shift valve in the oil pressure control device. It is alsoavailable that each shift range is electrically controlled by the ECU.

[0066] As mentioned above, in the case of the manual mode, a shift gearof the lowest gear ratio can be manually selected, while the shift leveris fixed to M position. Generally, when a vehicle runs at a constantspeed, since the shift position set at the running condition determinesthe highest gear among available shift gears of an automatictransmission, the highest gear among available shift gears is changed bymanually switching operation, and the gear shift occurs. That is, achanging of a shift range of the automatic transmission in M position isin substance a manual shift. In the manual shift mode, the shift deviceSr is fixed. A manual valve is then fixed. The shift range is selectedby an electric control signal from the ECU.

[0067] 6^(th) gear, that is the second gear of the overdrive gears, cannot be set in the automatic shift mode in which the shift device Sr isselected to D position. This means that 6^(th) gear is prohibited. Onthe contrary, 6^(th) gear can be set in the manual shift mode in whichthe shift device Sr is selected to M position, and the up-switch isoperated. That is, 6^(th) gear is permitted. FIG. 10 shows a part of ashift pattern map which sets a shift gear range of 6^(th) gear. Theshift gear range of the shift pattern map is determined by a vehiclespeed (the horizontal line in FIG. 10) and a throttle angle θ (thevertical line in FIG. 10). The solid line shows an up-shift, and thedotted line shows a down-shift. A shift gear is changed when the runningcondition of the vehicle crosses each line of the above-mentioned lines.The 6^(th) shift gear range is set in the higher speed side and in thelower throttle angle side than the shift 5^(th) gear range.Consequently, 6^(th) gear is set in the range in which the engine loadis low and the vehicle speed is high (ex. 120˜130 km/h or more). On thecontrary, when the position or the shift gear range in which 5^(th) gearis the highest is selected, a shift pattern map which does not include a6^(th) gear range is adopted, and a gear shift is executed according tothis shift pattern map. That is, 6^(th) gear is not set in this case.

[0068] In FIG. 11 a part of a lock-up pattern map for controlling anengagement or a disengagement of the lock-up clutch 15 is shown. In thiscase, the lock-up clutch 15 is controlled based on the lock-up patternmap when 6^(th) gear is set. The engagement range of the lock-up clutch15 is set in a high vehicle speed and a low throttle angle.Incidentally, the solid line an engagement of the lock-up clutch 15, andthe dotted line indicates a disengagement of the lock-up clutch 15. Whenthe driving condition in 6^(th) gear crosses each line of these lines,the lock-up clutch 15 is engaged or disengaged.

[0069] The above-mentioned embodiment is one example in which a shiftgear range is changed by a switch operation in M position. It is alsoavailable that a shift gear is selected by a manual operation, as shownin FIG. 9. That is, at each position from D to L position a shift gearis controlled in the automatic shift mode according to the drivingcondition. In M position, one gear is manually up-shifted, and one shiftgear among six shift gears is set by an operation of the up-switch 20.In the same way, in M position one gear is manually down-shifted, andone shift gear among six shift gears is set by an operation of thedown-switch 19. It is also available that these operations are executedby selecting the shift device Sr to the up position or the downposition, as shown in FIG. 7. On the basis of the signals of theseswitches, the ECU outputs a shift signal which orders one gear up-shiftor one gear down-shift from the current shift gear. That is, the gearratio is directly selected by a driver's intention in the manual shiftmode. In the manual shift mode, the shift device Sr is fixed. A manualvalve is then fixed. The gear shift is electrically selected by theelectric control signal from the ECU.

[0070] In this case as shown in FIG. 9, 5^(th) gear is the highest inthe automatic shift mode, and 6^(th) gear is the highest in the manualshift mode when M position is selected. This means that 6^(th) gear canbe set only by a manual operation of a driver.

[0071] The following signals are inputted or outputted to the electriccontrol unit ECU in order to control the gear shift at each shiftposition: the shift gear range by the switch operation in M position,the engagement or disengagement of the lock-up clutch 15, and oilpressure to each friction member or each clutch. That is, a signal froma turbine rotation speed NT sensor 16, a signal from an ABS (Anti-lockBrake System) computer, a signal from VSC (Vehicle Stability Control)computer, a signal of an engine revolution NE, a signal of an enginewater temperature, a signal from an ignition switch, a signal of abattery SOC (State Of Charge), an on-off signal from a head light, asignal from a defogger, an on-off signal from an air conditioner, asignal of a vehicle speed, a signal of an automatic transmission oiltemperature, a signal of a shift lever position, an on-off signal from aside brake, an on-off signal from a foot brake, a signal of a catalysttemperature, a signal of an accelerator angle, a signal from a camsensor, a + signal from the up-switch 20, a − signal from thedown-switch 19, a signal from a vehicle accelerator sensor, a lasersignal, a laser cruise setting signal, etc. are inputted to the ECU, asshown in FIG. 12. Incidentally, the battery SOC detects a condition of abattery which supplies an electric power to the above-mentioned motorinstalled in the hybrid vehicle or in the electric vehicle, or storesregenerated electricity in the case where a vehicle is a hybrid or anelectric vehicle. The detected results are sent to the ECU forcontrolling on the basis of the detected results. The laser signal andthe laser cruise setting signal are sent to the ECU for detecting avehicle running ahead by using a laser radar and for automaticallyfollowing the vehicle ahead while keeping a predetermined distancebetween the vehicle having this automatic transmission and the vehicleahead.

[0072] The output signals are an ignition signal, an injection signal, asignal to an AT (Automatic Transmission) solenoid, a signal to an inputclutch control solenoid, a signal to an AT line pressure controlsolenoid, a signal to an ASB actuator, a signal to a sport modeindicator, a signal to a VSC actuator, a signal to AT lock-up controlsolenoid, a signal to the second overdrive gear (6^(th) gear) indicator,etc. Incidentally, the above-mentioned input clutch selectively connectsor disconnects the engine to the drive line (the automatic transmission,etc.) in a vehicle having an economic running device or the hybridvehicle. The economic running device automatically suspends the engineto rotate and restarts the engine, when the vehicle temporarily stops,and saves consumed fuel in this way.

[0073] As mentioned above, the gear ratio of the 6^(th) gear is twogears higher than a direct connected condition (4^(th) gear) which gearratio is 1. That is, 6^(th) gear is two gears higher overdrive gear.Thus, the gear ratio of 6^(th) gear is considerably small, and theoutput torque from the automatic transmission is low. Consequently,6^(th) gear is only set in high speed and a low throttle angle. Sincethe engine revolution can be restrained low at high speed, the fuelefficiency at high speed can be improved. On the contrary, the engineload increases a little bit (this fact is shown as an increase of thethrottle angle), and the down-shift tends to happen easily when thevehicle speed becomes slightly lower. Furthermore, subsequently theup-shift tends to happen. That is, the “busy-shift” easily happens.

[0074] In a control device as a first embodiment of this presentinvention, 6^(th) gear as the second overdrive gear is controlled asfollows. FIG. 1 is a flowchart which explains the control device of thefirst embodiment. First, input signals are treated (Step S1), and it isdetermined which is a position selected by the shift device Sr, whetherD, “4”, “3”, “2”, or L position (Step S2). This determination isexecuted based on a signal from, for example, a switch attached on theshift device Sr. These shift positions are set in the automatic shiftmode. When one of these positions are selected by the shift device Sr,that is “yes” is determined in Step S2, the shift gear range is setaccording to the shift position (Step S3). The shift gear control isexecuted on the basis of the shift pattern map having a shift gear rangein the automatic shift mode shown in FIG. 8.

[0075] When “no” is determined in Step S2, whether M position isselected by the shift device Sr or not is determined (Step S4). If “no”is determined in Step 4, any control is not done and the step goes to“return”. This means that the vehicle is not in the forward drivingcondition. If “yes” is determined in Step S4, whether + switch is on ornot is determined (Step S5). This operation is done by turning on theup-switch 20 while holding the M position in the example shown in FIGS.5 and 6. Incidentally, the shift lever of the shift device Sr is movedto + position in another example shown in FIG. 7.

[0076] When the up-shift is executed, that is “yes” is determined inStep S5, the gear shift range in which 6^(th) gear (the second overdrivegear) is available is set in the manual shift mode (Step S6). That is,the shift pattern map, (one part of which is shown in FIG. 10) is takenup, and the gear shift is controlled based on this map. Furthermore, thelock-up pattern map shown in FIG. 11 is taken up, and the lock-up clutch15 is controlled according to this map.

[0077] Since 6^(th) gear or the condition where 6^(th) gear is availableis set by manually switching in the above-mentioned control, that is thegear shift range is manually set, the gear shift after this operation isautomatically done on the basis of the driving condition and the shiftpattern map. Once a gear shift until 6^(th) gear is available in StepS6, an indicator which shows “ON” of the second overdrive gear (6^(th)gear) is turned on (Step S7).

[0078] Since the gear ratio of the second overdrive gear (6^(th) gear)which is set in the above-mentioned way is small, the driving torque isnot enough when the vehicle runs in 6^(th) gear. Consequently, thedown-shift easily happens by slightly pushing an acceleration pedal orother things. This causes the “busy shift” or an uncomfortable feeling.However, this can be avoided by operating the down-switch 19 or shiftingthe shift lever of the shift device Sr to “−” position. This operationselects the shift range which prohibits 6^(th) gear.

[0079] When M position is selected and the up-shift switch 20 is notturned on, that is “no” is determined in Step S5, a shift gear is setaccording to each shift gear range (Step S8). That is, a shift patternmap according to the shift gear range shown in the second line or thelower line from the second line shown in the diagram in the manual shiftmode in FIG. 8 is taken up, and the shift control is executed on thebasis of the shift pattern map. An indicator which shows 6^(th) gear isnot be “ON” in this condition, for example it is shown that the secondoverdrive (OD2 or 6^(th)) gear is “OFF” (Step S9).

[0080] In the above-mentioned embodiment of the control device, a shiftgear range is manually changed. It is, however, also available that ashift gear itself can be changed by operating the up-switch 20 ordown-switch 19 in the condition where M position is selected by theshift device Sr. Each shift gear in this case is shown in FIG. 9, andany gear from 6^(th) gear to 1^(st) gear is available in M position. Onthe other hand, in the other forward position except M position, a shiftgear is set based on a driving condition. That is the automatic shiftmode. Each shift gear in this case is a gear from 5^(th) gear to 1^(st)gear as shown in FIG. 9. In this case, 6^(th) gear (the second overdrivegear) is set by a manual selection. Consequently, if a driver feelsinconvenience caused by the small gear ratio of the shift gear and arather high running resistance of the vehicle, the driver can select theshift position which does not include 6^(th) gear. Such inconvenience,then, can be avoided.

[0081] Incidentally, the control means for Step S6 shown in FIG. 1 is ahighest gear control means.

[0082] Since the gear ratio of 6^(th) gear (the second overdrive gear)is small as mentioned above, the engine revolution is low at high speed.Consequently, the fuel economy of the engine improves. On the contrary,since the margin of driving torque is small in 6^(th) gear, thedown-shift from 6^(th) gear easily happens when the acceleration pedalis slightly more pushed. Therefore, it is desirable that 6^(th) gear isset by the manual operation intended by the driver. In theaforementioned first embodiment, 6^(th) gear can only be set in themanual shift mode.

[0083] In place of the above-mentioned examples, it is also availablethat a special D position (D6) having 6^(th) gear in an automatic shiftmode is independently set in addition to other positions. If 6^(th) gearis desired, it is necessary to select the special shift pattern by amanual operation. This example adopted to a control device of the secondembodiment is explained as follows.

[0084] The shift positions selected by the shift device Sr are shown inFIG. 13. D5 position in which a shift gear from 5^(th) to 1^(st) gear isavailable is located next to N position. “4” position is located next toD5 position. “3”, “2”, L positions are disposed in series. The shiftdevice Sr is guided to each position along a path 18. In “4” positioneach shift gear from 4^(th) to 1^(st) gear can be set. In “3” positioneach shift gear from 3^(rd) to 1^(st) gear is available. In “2” position2^(nd) gear or 1^(st) gear is available. In L position 1^(st) gear canonly be set.

[0085] On the other hand, D6 position as the second drive position isdeposited at the opposite side of the “4” position, putting D5 positionbetween “4” and D6 positions. In other words, N, D6, and “4” positionsare deposited in the three different directions, and separately branchoff from D5 position. Each position is connected by the guiding path 18.

[0086] In a usual driving, the shift lever of the shift device Sr isshifted from P position to D5 position. When a vehicle accelerates ordecelerates, the shift lever is shifted to a preferable position from“4” position to L position. Each position from P position to L positionis connected by the guiding path 18, though the guiding path 18 ispartially turned at right angles or diagonally. On the other hand, D6position branches off from the above-mentioned guiding path 18 from Pposition to L position.

[0087] The control device, as the second embodiment, having theabove-mentioned shift positions is explained using FIG. 14. First, aninput signal is treated (Step S11). Next, whether the first driveposition D5 is selected or not is determined (Step S12). When “yes” isdetermined in Step S12, the first overdrive (OD1) gear shift pattern inwhich a shift gear from 1^(st) until 5^(th) gear is available is set(Step S13). Specifically, a shift pattern map in which the shift gearrange is shown is taken up, and a gear shift is executed based on theshift pattern map. Since the highest gear in the shift pattern map is5^(th) gear and the driving torque is sufficient, the busy shift doesnot happen.

[0088] On the other hand, when “no” is determined in Step S112 (thefirst drive position D5 is not selected), whether the second driveposition D6 is selected or not is determined (Step S14). If “yes” isdetermined in Step S14, a shift pattern map of the second overdrive(OD2) is set, where a shift gear from 6^(th) gear to 1^(st) gear isavailable. Specifically, the shift pattern map in which 6^(th) gearrange is set as shown in FIG. 10 is taken up, and a shift control isexecuted on the basis of the map. At the same time the lock-up patternmap shown in FIG. 11 is taken up. Since 6^(th) gear is set in the highspeed running, the engine revolution is low. Consequently, a fueleconomy of the engine is improved. Furthermore, since a margin drivingtorque in 6^(th) gear is small, a down-shift easily happens by a slightincrease of the acceleration angle or a slight decrease of the vehiclespeed.

[0089] If “no” is determined in Step S14 because the second driveposition D6 is not selected, the gear shift pattern of each position isset (Step S16).

[0090] As mentioned above, in the second embodiment 6^(th) gear (thesecond overdrive gear) can be set by selecting the second drive positionD6 deposited at the opposite direction from “4” position. D6 position islocated apart from the normal path of the shift lever Lv. The normalpath is used in a usual driving, in acceleration and deceleration, or ina “garage shift” driving. The shift lever of the shift device Sr isfrequently changed from D5 position to R position and vice versa in thegarage shift driving. Consequently, it is necessary to operateintentionally in order to set 6^(th) gear. Even though driving torque isnot sufficient in 6^(th) gear, the driver already is aware of andaccepts this fact. Accordingly, since this is not an unexpected drivingcondition for the driver, the driver does not feel uncomfortable. Inorder to avoid this driving condition it is recommendable to shift theshift lever of the shift device Sr from D6 to D5 position. By thisshift, 6^(th) gear is prohibited in D5 position, and the uncomfortabledriving feeling can be avoided.

[0091] Incidentally, it is also available that the second drive positionD6 is provided in a shift device which has M position, as shown in FIG.15. This example is also adopted to the control device of the secondembodiment. In this case D6 position separately branches off from thenormal path 18 connecting P, R, N, D5, “4”, “3”, “2”, and L position.The path 18 also connects D6 to D5 position. Since the driver needs tointentionally set 6^(th) gear in this case, the 6^(th) gear drivingcondition and the frequent gear change is acknowledged by the driver.The busy shift can be avoided by moving the shift lever of the shiftdevice Sr.

[0092] The first drive position D5 corresponds to a highest gearprohibition position, the second drive position D6 to a highest gearpermission position, and “4” position to a middle speed position.

[0093] A gear shift in an automatic transmission At is controlled on thebasis of the above-mentioned shift pattern map. Accordingly, if theshift pattern map is changed, the gear shift is executed in thedifferent shift pattern. The changed shift pattern map includes eachdifferent shift gear range, that is the number of available shift gearsis different in the different gear range. The shift pattern map can bechanged by taking up restored memories in the ECU.

[0094] As a control device of a third embodiment, one example ofchanging the shift pattern map or the shift pattern is next described.Referring to the flowchart in FIG. 18, after treating an input signal(Step S21), whether D position is selected or not is determined (StepS22). When D position is not selected, that is “no” is determined, theshift pattern according to the selected position is set. Consequentlythe step goes to “return”. On the contrary, when D position is selected(“yes” is determined), whether OD2 cut shift pattern is set or not isdetermined (Step S23). In OD2 cut shift pattern, 6^(th) gear as thesecond overdrive gear is not set. That is, it is electrically detectedand determined whether the shift pattern which prohibits 6^(th) gear isset or not, while holding the shift lever of the shift device Sr in theD position.

[0095] When “no” is determined in Step S23, that is the shift pattern inwhich 6^(th) gear is available is taken, whether there is a high speedclimbing driving condition ahead of a vehicle or not is determined by aNAVI (Navigation System installed in the vehicle), in other words adriving instruction system (Step S24). The NAVI in advance memorizeselectronic data of a road map, detects the position of the drivingvehicle by a GPS (Global Positioning System) or a self-navigation systemusing a gyro sensor, and displays the vehicle's position on an electricmap. Furthermore, the NAVI shows a recommended driving course from apresent position to an inputted destination, and a condition of the roadinstructed by the NAVI or the road ahead is also outputted. The roadcondition indicates curve or straight, a degree of the curvature, a kindof the road, a climbing or a down slope, an inclination of the slope,paved or not, a coefficient of friction of the road, etc. Incidentally,a conventional NAVI can be adopted. Since the NAVI can detect thescheduled course and the road condition of the scheduled course, whetherthe road ahead is for a high speed driving and whether the inclinationof the slope is equal to or over a predetermined value can be determinedin Step S24.

[0096] When “yes” is determined, that is the vehicle is running in6^(th) gear which is the highest gear of the automatic transmission,whether a gear shift occurs or not when 6^(th) gear is prohibited isdetermined (Step S25). This is a preparatory determination for highspeed climbing. If a down-shift occurs when 6^(th) gear is prohibited, adriver feels uncomfortable, because the gear shift is not causedintentionally. Therefore, the step proceeds to “return” in order toavoid this uncomfortable feeling. On the other hand, when “no” isdetermined in Step S25, that is gear shift does not occur, an OD2 cutshift pattern which prohibits the second overdrive gear (6^(th) gear) isset (Step S26). Specifically, a shift pattern map which does not have ashift gear range of 6^(th) gear is taken up, and the shift control isexecuted on the basis of the shift pattern map.

[0097] When “no” is determined in Step S24, a high speed climbing isdetermined by an actual driving condition (Step S27). Whether thevehicle runs at high speed or not is determined by detecting whether theactual speed is equal to or over a predetermined value or not. Whetherthe inclination of the slope is equal to or over a predetermined value(that is, the running resistance of the vehicle is equal to or over apredetermined value) is determined by detecting whether the actualacceleration is equal to or less than a standard value based on athrottle angle or not. Incidentally, since the inclination of the slopeof the high speed road does not increase suddenly, whether a high speedslope is ahead in the scheduled course can also be determined based on adecreasing rate of the acceleration of the vehicle.

[0098] When “yes” is determined in Step S27, as the same as “yes” isdetermined in Step S24, the step proceeds to Step S25. Whether a gearshift occurs or not if 6^(th) gear is prohibited is, here, determined.If the gear shift does not occur, the OD2 cut shift pattern (that is,6^(th) gear is prohibited.) is set. On the contrary, if it is determinedthat the shift occurs, the step goes to “return”.

[0099] When “yes” is determined in Step S23, because the above-mentionedStep S26 is already executed, a reversion from the OD2 cut shift patternis next done. That is, whether a road ahead requires a high speedclimbing condition is determined by the NAVI (Step S28). When “yes” isdetermined in Step S28, any shift gear change is not executed and thestep goes to “return”, in order to keep 6^(th) gear prohibited, that isin order to continue the previous control.

[0100] On the contrary, when “no” is determined in Step S28, that isthere is not a road ahead for a high speed climbing, whether there issuch a high speed climbing road or not is determined by actual drivingconditions, such as an actual vehicle speed and/or an actualacceleration of the vehicle (Step S29). Since an inclination of the highspeed road does not decrease suddenly in this case, whether the highspeed climbing road ends or not can also be predicted on the basis of anincreasing rate of the acceleration. If “yes” is determined, that is thehigh speed climbing road continues, in Step S29, the step proceeds to“return” without any control, and in order to keep 6^(th) gearprohibited, in the same way as the case where “yes” is determined inStep S28.

[0101] On the other hand, if “no” is determined in Step S29, this meansthe high speed climbing road ends. It is then determined whether a gearshift occurs or not when a shift pattern where 6^(th) gear is availableis selected (Step S30). When the gear shift occurs when the shiftpattern is changed in Step S30, the step proceeds to “return” withoutany control in order to avoid an unexpected gear shift. On the otherhand, however, when it is denied in Step S30 that the gear shift occurs,the OD2 shift pattern where 6^(th) gear can be set is selected. (StepS31). Specifically, the above-mentioned shift pattern map shown in FIG.10 is taken up, and the shift control is executed based on the shiftpattern map. In this case, the lock-up map shown in FIG. 11 whichcontrols the lock-up clutch 15 can be selected.

[0102] Since the vehicle runs in 5^(th) gear in which the vehicle hasenough driving torque when the vehicle runs on the high speed climbingroad, the down-shift does not easily occur if the acceleration pedal isslightly pushed to maintain the current vehicle speed or etc.Consequently, the busy shift can be avoided. Furthermore, since thesecond overdrive gear (6^(th) gear) can be set when the high speedclimbing road ends, a fuel consumption can be reduced because the enginerevolutions reduce at high speed.

[0103] Explaining the relation between this example and the presentinvention, the above-mentioned navigation system (NAVI) corresponds to adriving instruction system, and the means for setting OD2 (6^(th) gear)cut shift pattern corresponds to a highest gear prohibition means.

[0104] Next, a control device of a fourth embodiment of the invention isdescribed. It is also available that a vehicle having the control deviceof this present invention is controlled to follow another vehicle ahead.In the following control, another vehicle is detected by a radar systemsuch as a laser radar, and a predetermined distance between the vehiclehaving the radar system and another vehicle ahead is maintained. Athrottle angle or a gear ratio of an automatic transmission mounted onthe vehicle with the radar system is controlled so that the vehiclespeed and the aforementioned distance is maintained. Since it is desiredthat a response of an accelerating or decelerating control is quick inthis following driving, the control is executed as follows.

[0105] The shift positions shown in FIG. 16 are adopted to the controldevice of the fourth embodiment. The shift positions selected by theshift device Sr are arranged deposited, as shown in FIG. 16. P, R, N, D,“5” “4”, “3”, “2”, and L positions are located in series. Each positionis connected by a guiding path 18. Available shift gears in the forwarddriving position from D to L position are shown in FIG. 17. When Dposition is selected, a shift gear from 6^(th) to 1^(st) gear is setbased on the driving condition. From “5” to L position the highest gearin each position is one gear lower respectively. In changing eachposition the shift control is executed by taking up the shift patternmap having each shift gear range responding to each position, and bytreating a respective output signal.

[0106]FIG. 19 is a flowchart of the control device as the fourthembodiment. An automatic transmission mounted on a vehicle which has afollowing control system has six forward gears including 5^(th) and6^(th) gears, as overdrive gears. Another example of shift positionssetting those shift gears is shown in FIG. 20. For forward driving D,“4”, “3”, “2”, and L positions are provided. Each shift gear which canbe set in each position is shown in FIG. 20. Incidentally, in thisexample shown in FIG. 20, all six shift gears from 1^(st) to 6^(th) gearcan be set in D position as the same as the above-mentioned examples,but “5” position is not provided.

[0107] After a treatment of an input signal in FIG. 19 (Step S41),whether D position is selected by the shift device Sr or not isdetermined (Step S42). In D position, as shown in FIG. 20, a forwarddriving shift gear is set on the basis of a driving condition of thevehicle. When “no” is determined in Step S42 because a shift positionexcept D position is selected, the following drive system is prohibited(Step S43). If N position is selected, the following drive system isprohibited. Furthermore, even though a forward drive position isselected, in a position except D position (in such a position an enginebrake is available) the highest gear is 4^(th) gear or the lower gear.Consequently, this condition is not suitable for the following drive.When a position except D position is selected, therefore, the followingdrive system by itself is prohibited.

[0108] Incidentally, if the following drive is suitable in 4^(th) gear(the highest gear in “4” position), it is also available that thefollowing drive system is not prohibited when “4” position is selected.

[0109] On the contrary, when D position is selected (“yes” in Step S42),whether a laser cruise switch is turned on or not is determined (StepS44). “On” of the laser cruise switch means that another vehicle aheadis detected by the laser radar mounted in a vehicle and is followed withmaintaining a predetermined distance between the vehicle and anothervehicle ahead. When the laser cruise switch is not turned on in StepS44, a shift pattern in which the second overdrive gear (OD2, that is6^(th) gear) is available is selected (Step S45). On the other hand“yes” (the switch is on) is determined in Step S44, a shift pattern inwhich 5^(th) gear is the highest, that is 6^(th) gear is prohibited, isset (Step S46). In this case, the highest (6^(th)) gear is prohibited,when a mode of following another vehicle begins (that is, the lasercruise switch is turned on).

[0110] Incidentally, it is also available that the highest gear isprohibited, when the vehicle actually begins to follow another vehicle.

[0111] Specifically, in the case where D position is selected and thefollowing drive system is not executed, the shift pattern map in which6^(th) gear range is set as shown in FIG. 10 is taken up, and the shiftcontrol is executed. At the same time the lock-up map shown in FIG. 11is read, and the lock-up clutch 15 is controlled in the condition where6^(th) gear is set. Since the engine revolutions are reduced at highspeed, fuel efficiency improves. On the contrary, in the following drivea shift pattern in which 6^(th) gear range is excluded from the shiftpattern shown in FIG. 10 is taken up, and the gear shift is controlledbased on this modified shift pattern. Since the highest gear is 5^(th)gear, then, the gear ratio of the automatic transmission at high speedis not so small (even though less than 1). Consequently, a certainextent amount of driving torque is secured. Therefore, a response infollowing another vehicle ahead is improved.

[0112] One example of vehicles which respectively include theabove-mentioned automatic transmissions is schematically shown in FIG.21.

[0113] The means for executing the control shown in FIG. 19 correspondsto a highest gear prohibition means.

[0114] As mentioned above, the embodiments are explained based on theexamples shown in the above-mentioned figures. It is not limited tothese embodiments. That is, an automatic transmission which has three ormore overdrive gears is also available. The gear ratios of the overdrivegears are less than 1. It is not limited to the gear train arrangementshown in FIG. 2. Furthermore, a continuously variable transmission whichdoes not have a finite number of shift gears is also available.Furthermore, the transmission mounted on a vehicle which includes anelectric motor or a motor generator as a driving power source in placeof the internal combustion engine, is also available.

[0115] The shift device Sr which selects each shift position is providedfor changing each oil pressure supplying to each passage according toeach shift position. Consequently, it is also available that a shiftdevice outputs an electric signal by a manual operation, such as aswitch lever, in place of the shift lever mechanically connecting toeach manual valve. That means the present invention can also be adoptedto a control device for a “shift by wire” type automatic transmission.

[0116] Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein. It is intended that the specificationand examples be considered as exemplary only, with the true scope andspirit of the invention being indicated by the following claims.

What is claimed is:
 1. A control device for an automatic transmissioncomprising: a selecting device for selecting an automatic shift mode forautomatically determining a gear ratio of the automatic transmission onthe basis of a driving condition of a vehicle having the automatictransmission or an independent manual shift mode for reflecting adriver's intention for determining a gear ratio of the automatictransmission; and a highest gear control means for controlling theautomatic transmission so that the smallest gear ratio set by saidmanual shift mode is smaller than the smallest gear ratio set by saidautomatic shift mode.
 2. The control device for the automatictransmission according to claim 1, wherein one of a plurality of shiftranges each having a pre-set number of automatically selected gearratios is selected by the driver in said manual shift mode.
 3. Thecontrol device for the automatic transmission according to claim 2,wherein the shift range is electrically controlled by an electriccontrol unit in the automatic transmission.
 4. The control device forthe automatic transmission according to claim 1, wherein the gear ratiois directly selected by the driver in said manual shift mode.
 5. Thecontrol device for the automatic transmission according to claim 4,wherein the gear ratio is electrically controlled by an electric controlunit in the automatic transmission.
 6. The control device for theautomatic transmission according to claim 1, wherein the highest gear ofthe automatic transmission is an overdrive gear.
 7. A control device foran automatic transmission comprising: a shift device for selecting: aneutral position wherein the automatic transmission does not output atorque to an output shaft of the automatic transmission, a highest gearprohibition position wherein the highest gear of the automatictransmission is prohibited, a highest gear permission position whereinthe highest gear of the automatic transmission is allowed, and a middlespeed position wherein a gear ratio can be set between the largest gearratio and a predetermined gear ratio larger than the smallest gear ratioof said highest gear prohibition position; and a means for guiding saidshift device along a path to the neutral position, a path to the highestgear permission position, and a path to the middle speed position, eachpath to the neutral position, the highest gear permission position, andthe middle speed position separately branching off from the highest gearprohibition position.
 8. The control device for the automatictransmission according to claim 7, wherein the highest gear of theautomatic transmission is an overdrive gear.
 9. A control device for anautomatic transmission comprising: a plurality of gears including anoverdrive gear; and a highest gear prohibition means for prohibiting thesmallest gear ratio of the overdrive gears of the automatic transmissionwhen a running resistance of the vehicle is equal to or over apredetermined value.
 10. The control device for the automatictransmission according to claim 9, wherein the plurality of gearsincludes a plurality of overdrive gears.
 11. The control device for theautomatic transmission according to claim 9, wherein the highest gearprohibition means prohibits the smallest gear ratio of the overdrivegears of the automatic transmission when a speed of a vehicle having theautomatic transmission is equal to or over a predetermined value.
 12. Acontrol device for an automatic transmission installed in a vehiclehaving a driving instruction system, said driving instruction systemdetecting a predetermined scheduled course for driving the vehicle and aroad condition of the predetermined scheduled course, said controldevice comprising: a means for controlling a gear shift of the automatictransmission on the basis of the road condition of the predeterminedscheduled course; and a highest gear prohibition means for prohibitingthe smallest gear ratio of the automatic transmission when the vehicleis driven on the predetermined scheduled course, a speed of the vehicleis equal to or over a predetermined value, and a running resistance ofthe vehicle is equal to or over a predetermined value.
 13. The controldevice for the automatic transmission according to claim 12, wherein thehighest gear of the automatic transmission is an overdrive gear.
 14. Thecontrol device for the automatic transmission according to claim 12,wherein said driving instruction system conjectures a slope from roadmap information and said highest gear prohibition means prohibits thesmallest gear ratio of the automatic transmission before the slope. 15.The control device for the automatic transmission according to claim 12,wherein said driving instruction system conjectures a slope from anacceleration or a deceleration of the vehicle and said highest gearprohibition means prohibits the smallest gear ratio of the automatictransmission when the slope is conjectured.
 16. The control device forthe automatic transmission according to claim 12, wherein said highestgear prohibition means prohibits the smallest gear ratio of theautomatic transmission without delay if a shift gear of the automatictransmission does not change when a slope is ahead.
 17. The controldevice for the automatic transmission according to claim 12, whereinsaid highest gear prohibition means prohibits the smallest gear ratio ofthe automatic transmission without delay if a shift gear of theautomatic transmission does not change and prohibits the smallest gearratio of the automatic transmission with delay when a slope is ahead.18. A control device for an automatic transmission installed in avehicle, said vehicle having a following device for following anothervehicle ahead, the control device comprising: a shift device; and ahighest gear prohibition means for prohibiting the smallest gear ratioof the automatic transmission when the vehicle is driven by thefollowing device.
 19. The control device for the automatic transmissionaccording to claim 18, wherein the highest gear of the automatictransmission is an overdrive gear.
 20. The control device for theautomatic transmission according to claim 18, wherein the vehicle ispermitted to follow another vehicle when the shift position of theautomatic transmission is D position.
 21. The control device for theautomatic transmission according to claim 18, wherein the highest gearis prohibited when a following mode of said following device begins.